I don't agree with one case of this. I think there is a need to have IPv6 only hosts that are able to reach the same IPv4 services that an IPv4 host behind a NAT today can reach. This will make IPv6 only hosts much more attractive than if they can only reach IPv6 services. This will make IPv6 only a real possibility for new deployments of new types of devices. If we don't support this case, then these devices (and resulting infrastructure) will have to be dual stack.i don't think we should try to solve the problem of an arbitrary user/service on a pure v6 site/host trying to communicate with a user/service on a pure v4 site/host or vice versa.I agree with this.